Foldable electrophoretic display module including non-conductive support plate

ABSTRACT

A foldable electrophoretic display that is flexible and may be folded in a book-like fashion. Foldable electrophoretic display modules that can be separately manufactured and incorporated into a variety of foldable devices with differing functionality as needed by the consumer. In some embodiments, the resulting foldable electrophoretic display may include touch sensing, a front light, color, and a digitizing layer to record interactions with a stylus. In some embodiments, the display includes a color filter array.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 63/033,954, filed Jun. 3, 2020, which is incorporated by referencein its entirety. All patents and publications disclosed herein areincorporated by reference in their entireties.

FIELD OF THE INVENTION

This invention relates to foldable electrophoretic displays, theformation of such displays, and component modules for the manufacture offoldable electrophoretic displays. Integrated foldable electrophoreticdisplay modules can be fabricated in one location and then shipped to adifferent manufacturing facility where different components, providingdifferent functionality, can be incorporated into the final foldabledisplay. Such differing functionality may include, e.g., different typesof front lights, different types of touch sensing, or different types ofstylus recognition, depending upon the needs of the consumer and thedesired price point.

BACKGROUND OF INVENTION

In some instances, a flexible display may be folded for portabilityand/or convenience of storage. If the display was simply folded in abook like fashion, it may be folded with a radius of curvature that issmaller than a minimum radius of curvature designed to prevent displaybreakage. To prevent such problem, various mechanisms, such as hingesand/or other structures, have been implemented to the bending portionsof the display. For example, Polymer Vision has disclosed a productReadius™ using one or more mechanical hinge mechanisms to facilitate thefolding of the flexible display.

In another example, Japanese Patent Laid-Open Publication No.2014-161009 discloses a flexible mobile terminal device configured tobend at various angles. The terminal device is proposed to include afolding portion for bending the device to a front surface or a rearupper position of a terminal device body. A flexible display mounted onan upper portion of the terminal device body can be bend to the frontsurface or a rear surface depending on a bending direction of thefolding portion. The device further includes a sliding portion forcausing one end of the flexible display to slide by a difference betweendegrees of compression/tension generated by a difference in extensionrates of the folding portion and the flexible display during bending ofthe folding portion.

Both examples described above result in thick and heavy products. TheReadius™ by Polymer Vision employs mechanical hinge mechanisms that arecomplex in structure and bulky in shape. The device of Japanese PatentLaid-Open Publication No. 2014-161009 has a bellows shape and thesliding portion takes labor to adjust, and the device is also complexand bulky.

In addition to being bulky and thick, an additional shortcoming of thedevices described above is that such designs make it difficult tointegrate all of the functionality that consumers expect in a premiumelectrophoretic display device, such as touch sensing, front light,stylus recognition, and color.

SUMMARY OF INVENTION

In response to these needs, the disclosure describes a foldableelectrophoretic display module and a variety of foldable electrophoreticdisplays that incorporate the foldable electrophoretic display moduleand provide a variety of sensing functionality. In a first aspect, theinvention includes an electrophoretic display module, including asupport plate having material voids in a central folding zone, a layerof low-modulus adhesive adjacent the support plate, a flexible backplanethat spans the central folding zone and is adjacent the layer oflow-modulus adhesive, a layer of electrophoretic display media adjacentthe flexible backplane, and a conductive integrated barrier layerincluding a light-transmissive electrode and a moisture barrier. In someembodiments, the electrophoretic display module additionally includes aprotection layer between the layer of low-modulus adhesive and theflexible backplane. In some embodiments, the flexible backplanecomprises an active matrix of organic-thin-film-transistors. In someembodiments, the electrophoretic display module additionally includes anedge seal coupled to the flexible backplane, the layer ofelectrophoretic display media, and the conductive integrated barrier. Insome embodiments, the layer of electrophoretic display media iscontained in a layer of microcells. In some embodiments, the layer ofelectrophoretic display media is contained in microcapsules and themicrocapsules are held in place by a polymer binder. In someembodiments, the electrophoretic display module additionally includes aprotective sheet adjacent the conductive integrated barrier. In someembodiments, the electrophoretic display module additionally includes anedge seal coupled to the flexible backplane, the layer ofelectrophoretic display media, the conductive integrated barrier, andthe protective sheet. In some embodiments, the support plate comprises anon-conductive polymer. In some embodiments, the support plate isbetween 250 μm and 50 μm in thickness.

In a second aspect, the invention includes a foldable electrophoreticdisplay configured to interact with a stylus, the foldable displayincluding a support plate having material voids in a central foldingzone, a layer of low-modulus adhesive adjacent the support plate, aflexible backplane that spans the central folding zone and is adjacentthe layer of low-modulus adhesive, a layer of electrophoretic displaymedia adjacent the flexible backplane, and a conductive integratedbarrier layer including a light-transmissive electrode and a moisturebarrier, a protective sheet coupled to the conductive integratedbarrier, an electromagnetic resonance (EMR) sensor layer adjacent to thesupport plate, a foldable chassis adjacent to the EMR sensor layer, anda housing surrounding the foldable chassis and providing a bezelcontacting the protective sheet, and allowing a user to view theelectrophoretic display medium through the protective sheet. In someembodiments, the foldable electrophoretic display additionally includesan intermediate layer of a low-modulus adhesive disposed between the EMRsensor layer and the support plate. In some embodiments, the foldableelectrophoretic display additionally includes an intermediate layer of ahigh-modulus adhesive disposed between the EMR sensor layer and thesupport plate. In some embodiments, the intermediate layer of alow-modulus adhesive and the intermediate layer of a high-modulusadhesive do not span the central folding zone. In some embodiments, thefoldable electrophoretic display additionally includes a touch sensitivelayer disposed between the EMR sensor layer and the foldable chassis. Insome embodiments, the foldable electrophoretic display additionallyincludes an intermediate layer of a low-modulus adhesive disposedbetween the touch sensitive layer and the foldable chassis. In someembodiments, the foldable electrophoretic display additionally includesan intermediate layer of a high-modulus adhesive disposed between thetouch sensitive layer and the foldable chassis. In some embodiments, theintermediate layer of a low-modulus adhesive and the intermediate layerof a high-modulus adhesive do not span the central folding zone. In someembodiments, the conductive integrated barrier additionally comprises acolor filter array (CFA).

In a third aspect a foldable electrophoretic display configured tointeract with a stylus, including a support plate having material voidsin a central folding zone, a layer of low-modulus adhesive adjacent thesupport plate, a flexible backplane that spans the central folding zoneand is adjacent the layer of low-modulus adhesive, a layer ofelectrophoretic display media adjacent the flexible backplane, and aconductive integrated barrier layer including a light-transmissiveelectrode and a moisture barrier, a flexible front light plate coupledto the conductive integrated barrier, a flexible capacitive touch layeradjacent to the flexible front light plate, a protective sheet adjacentto the flexible capacitive touch layer, a foldable chassis adjacent tothe support plate; and a housing surrounding the foldable chassis andproviding a bezel contacting the protective sheet, and allowing a userto view the electrophoretic display medium through the protective sheet.In some embodiments, the foldable electrophoretic display additionallyincludes an intermediate layer of a low-modulus adhesive disposedbetween the foldable chassis and the support plate. In some embodiments,the foldable electrophoretic display additionally includes anintermediate layer of a high-modulus adhesive disposed between thefoldable chassis and the support plate. In some embodiments, theintermediate layer of a low-modulus adhesive and the intermediate layerof a high-modulus adhesive do not span the central folding zone. In someembodiments, the conductive integrated barrier additionally comprises acolor filter array (CFA).

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A shows an embodiment of a foldable electrophoretic displayincluding a support plate having material voids in a central foldingzone.

FIG. 1B shows an embodiment of a module for a foldable electrophoreticdisplay including a support plate having material voids in a centralfolding zone.

FIG. 2A shows an embodiment of a foldable electrophoretic displayincluding a support plate having material voids in a central foldingzone. The foldable electrophoretic display of FIG. 2A includes anelectromagnetic resonance (EMR) sensing layer to enable sensing of astylus.

FIG. 2B shows an embodiment of a foldable electrophoretic displayincluding a support plate having material voids in a central foldingzone. The foldable electrophoretic display of FIG. 2B includes anelectromagnetic resonance (EMR) sensing layer to enable sensing of astylus. One side of the electrophoretic display of FIG. 2B includeslow-modulus adhesive layers while the other side of the electrophoreticdisplay of FIG. 2B includes high-modulus adhesive layers. Accordingly,one side of the display stack is able to move laterally as the displayis folded.

FIG. 3 shows an embodiment of a foldable electrophoretic displayincluding a support plate having material voids in a central foldingzone. The foldable electrophoretic display of FIG. 3 includes acapacitive touch-sensing layer as well as a front light.

FIG. 4A shows a side view of an embodiment of a support plate havingmaterial voids in a central folding zone.

FIG. 4B shows a top view of an embodiment of a support plate havingmaterial voids in a central folding zone.

FIG. 5A shows a side view of an embodiment of a support plate havingmaterial voids in a central folding zone.

FIG. 5B shows a top view of an embodiment of a support plate havingmaterial voids in a central folding zone.

DETAILED DESCRIPTION

As indicated above, the present invention provides an electrophoreticdisplay that is flexible and may be folded in a book-like fashion andmodules for use in the production of making such foldable displays. Thedesign is thin and lightweight, and because the support plate isnon-conductive, it is possible to situate the support plate between theelectrophoretic display layer and an electromagnetic resonance sensingdevice.

The invention is well suited to be used with electrophoretic media ofthe type developed by E Ink Corporation (Billerica, Mass.) and describedin the patents and patent publications listed below. Encapsulatedelectrophoretic media comprise numerous small capsules, each of whichitself comprises an internal phase containing electrophoretically-mobileparticles in a fluid medium, and a capsule wall surrounding the internalphase. Typically, the capsules are themselves held within a polymericbinder to form a coherent layer positioned between two electrodes. In amicrocell electrophoretic display, the charged particles and the fluidare not encapsulated within microcapsules but instead are retainedwithin a plurality of cavities formed within a carrier medium, typicallya polymeric film. The technologies described in these patents andapplications include: (a) Electrophoretic particles, fluids and fluidadditives; see for example U.S. Pat. Nos. 7,002,728 and 7,679,814; (b)Capsules, binders and encapsulation processes; see for example U.S. Pat.Nos. 6,922,276 and 7,411,719; (c) Microcell structures, wall materials,and methods of forming microcells; see for example U.S. Pat. Nos.7,072,095 and 9,279,906; (d) Methods for filling and sealing microcells;see for example U.S. Pat. Nos. 7,144,942 and 7,715,088; (e) Films andsub-assemblies containing electro-optic materials; see for example U.S.Pat. Nos. 6,982,178 and 7,839,564; (f) Backplanes, adhesive layers andother auxiliary layers and methods used in displays; see for exampleU.S. Pat. Nos. D485,294; 6,124,851; 6,130,773; 6,177,921; 6,232,950;6,252,564; 6,312,304; 6,312,971; 6,376,828; 6,392,786; 6,413,790;6,422,687; 6,445,374; 6,480,182; 6,498,114; 6,506,438; 6,518,949;6,521,489; 6,535,197; 6,545,291; 6,639,578; 6,657,772; 6,664,944;6,680,725; 6,683,333; 6,724,519; 6,750,473; 6,816,147; 6,819,471;6,825,068; 6,831,769; 6,842,167; 6,842,279; 6,842,657; 6,865,010;6,873,452; 6,909,532; 6,967,640; 6,980,196; 7,012,735; 7,030,412;7,075,703; 7,106,296; 7,110,163; 7,116,318; 7,148,128; 7,167,155;7,173,752; 7,176,880; 7,190,008; 7,206,119; 7,223,672; 7,230,751;7,256,766; 7,259,744; 7,280,094; 7,301,693; 7,304,780; 7,327,511;7,347,957; 7,349,148; 7,352,353; 7,365,394; 7,365,733; 7,382,363;7,388,572; 7,401,758; 7,442,587; 7,492,497; 7,535,624; 7,551,346;7,554,712; 7,583,427; 7,598,173; 7,605,799; 7,636,191; 7,649,674;7,667,886; 7,672,040; 7,688,497; 7,733,335; 7,785,988; 7,830,592;7,843,626; 7,859,637; 7,880,958; 7,893,435; 7,898,717; 7,905,977;7,957,053; 7,986,450; 8,009,344; 8,027,081; 8,049,947; 8,072,675;8,077,141; 8,089,453; 8,120,836; 8,159,636; 8,208,193; 8,237,892;8,238,021; 8,362,488; 8,373,211; 8,389,381; 8,395,836; 8,437,069;8,441,414; 8,456,589; 8,498,042; 8,514,168; 8,547,628; 8,576,162;8,610,988; 8,714,780; 8,728,266; 8,743,077; 8,754,859; 8,797,258;8,797,633; 8,797,636; 8,830,560; 8,891,155; 8,969,886; 9,147,364;9,025,234; 9,025,238; 9,030,374; 9,140,952; 9,152,003; 9,152,004;9,201,279; 9,223,164; 9,285,648; and 9,310,661; and U.S. PatentApplications Publication Nos. 2002/0060321; 2004/0008179; 2004/0085619;2004/0105036; 2004/0112525; 2005/0122306; 2005/0122563; 2006/0215106;2006/0255322; 2007/0052757; 2007/0097489; 2007/0109219; 2008/0061300;2008/0149271; 2009/0122389; 2009/0315044; 2010/0177396; 2011/0140744;2011/0187683; 2011/0187689; 2011/0292319; 2013/0250397; 2013/0278900;2014/0078024; 2014/0139501; 2014/0192000; 2014/0210701; 2014/0300837;2014/0368753; 2014/0376164; 2015/0171112; 2015/0205178; 2015/0226986;2015/0227018; 2015/0228666; 2015/0261057; 2015/0356927; 2015/0378235;2016/077375; 2016/0103380; and 2016/0187759; and InternationalApplication Publication No. WO 00/38000; European Patents Nos. 1,099,207B1 and 1,145,072 B1; (g) Color formation and color adjustment; see forexample U.S. Pat. Nos. 7,075,502 and 7,839,564; and (h) Methods fordriving displays; see for example U.S. Pat. Nos. 7,012,600 and7,453,445. All of the patents and patent applications listed herein areincorporated by reference in their entirety. Many of the aforementionedpatents and applications recognize that the walls surrounding thediscrete microcapsules in an encapsulated electrophoretic medium couldbe replaced by a continuous phase, thus producing a so-calledpolymer-dispersed electrophoretic display, in which the electrophoreticmedium comprises a plurality of discrete droplets of an electrophoreticfluid and a continuous phase of a polymeric material, and that thediscrete droplets of electrophoretic fluid within such apolymer-dispersed electrophoretic display may be regarded as capsules ormicrocapsules even though no discrete capsule membrane is associatedwith each individual droplet; see for example, the aforementioned U.S.Pat. No. 6,866,760. Accordingly, for purposes of the presentapplication, such polymer-dispersed electrophoretic media are regardedas sub-species of encapsulated electrophoretic media.

An encapsulated electrophoretic display typically does not suffer fromthe clustering and settling failure mode of traditional electrophoreticdevices and provides further advantages, such as the ability to print orcoat the display on a wide variety of flexible and rigid substrates.(Use of the word “printing” is intended to include all forms of printingand coating, including, but without limitation: pre-metered coatingssuch as patch die coating, slot or extrusion coating, slide or cascadecoating, curtain coating; roll coating such as knife over roll coating,forward and reverse roll coating; gravure coating; dip coating; spraycoating; meniscus coating; spin coating; brush coating; air knifecoating; silk screen printing processes; electrostatic printingprocesses; thermal printing processes; ink jet printing processes;electrophoretic deposition (See U.S. Pat. No. 7,339,715); and othersimilar techniques.) Thus, the resulting display can be flexible.Further, because the display medium can be printed (using a variety ofmethods), the display itself can be made inexpensively.

While the invention is primarily directed to electrophoretic media ofthe type described above and in the listed patents and patentapplications, other types of electro-optic materials may also be used inthe present invention. The alternative electro-optic media are typicallyreflective in nature, that is, they rely on ambient lighting forillumination instead of a backlight source, as found in an emissive LCDdisplay. Alternative electro-optic media include rotating bichromalmember type media as described, for example, in U.S. Pat. Nos.5,808,783; 5,777,782; 5,760,761; 6,054,071 6,055,091; 6,097,531;6,128,124; 6,137,467; and 6,147,791. Such a display uses a large numberof small bodies (typically spherical or cylindrical) which have two ormore sections with differing optical characteristics, and an internaldipole. These bodies are suspended within liquid-filled vacuoles withina matrix, the vacuoles being filled with liquid so that the bodies arefree to rotate. The appearance of the display is changed by applying anelectric field thereto, thus rotating the bodies to various positionsand varying which of the sections of the bodies is seen through aviewing surface. This type of electro-optic medium is typicallybistable.

Another alternative electro-optic display medium is electrochromic, forexample an electrochromic medium in the form of a nanochromic filmcomprising an electrode formed at least in part from a semi-conductingmetal oxide and a plurality of dye molecules capable of reversible colorchange attached to the electrode; see, for example O'Regan, B., et al.,Nature 1991, 353, 737; and Wood, D., Information Display, 18(3), 24(March 2002). See also Bach, U., et al., Adv. Mater., 2002, 14(11), 845.Nanochromic films of this type are also described, for example, in U.S.Pat. Nos. 6,301,038; 6,870,657; and 6,950,220. This type of medium isalso typically bistable.

An exemplary foldable electrophoretic display (FEPID) is show in FIG.1A. Foldable display 10 normally comprises a layer of electrophoreticdisplay media 80 and at least two other conductive layers 75 and 90disposed on opposed sides of the layer of electrophoretic display media80. The stack of conductive layers and the layer of electrophoreticdisplay media 80 are disposed on a support plate 50 having materialvoids 55 in a central folding zone 57. Typically, the flexible backplane75 is coupled to the a support plate 55 with a low-modulus adhesive 60,which provides good adhesion between the layers so that the displaysurface remains flat when opened, but also allows enough lateralslippage so that the flexible backplane 75 can move slightly withrespect to the support plate 50 as the FEPID is opened and closed.Suitable low-modulus adhesives 60 may include adhesive foam polymersfrom 3M (Minneapolis, Minn.) and CGR Products (Greensboro, N.C.). Thelow-modulus adhesives may comprise polyurethanes, polyacrylates, and/orsilicones. Exemplary low-modulus adhesives may be known as PORON®, whichis a registered trademark of Rogers Corporation, or DOWSIL®, which is aregistered trademark of Dow Chemical Corporation. In some instances, thelow-modulus adhesives 60 provide compressive resistance between thesupport plate 50 and the flexible backplane 75. While FIG. 1A depicts alayer of low-modulus adhesive 60 that spans the central folding zone 57,it is also possible for the layer of low-modulus adhesive 60 to beinterrupted in the central folding zone 57, thereby providing more roomfor flexure of the portion of the support plate 50 having material voids55, i.e., in the central folding zone 57. The low-modulus adhesive layertypically is between 500 μm and 50 μm in thickness, for example, between300 μm and 100 μm in thickness.

While the support plate 50, alone, provides sufficient rigidity for afoldable display 10, a foldable display 10 typically additionallyincludes a chassis 20 that is coupled by a hinge 25 to providemechanical shock protection in addition to protecting the support platefrom being extended past flat (i.e., past 180° of opening) at whichpoint the flexible backplane 75 may fail because the flexible traces(not shown) in the flexible backplane 75 are stretched to a point thatthey break. The structure of the chassis may include a two-part chassis,as shown in FIG. 1A, however the chassis may include a three-part systemwhereby a central “spine” region is coupled to two different leafs withtwo different hinges, or a complex hinge that spans the three portions.Thus with the stack-up shown in FIG. 1A, a lightweight electrophoreticdisplay 10 is produced that can fold between flat (as shown) and closed,like a normal book.

In the instance of FIG. 1A, the top conductive layer has beenincorporated into a conductive integrated barrier layer 90, including alight-transmissive conductive material and a flexible moisture barrier.For example, the conductive integrated barrier layer 90 may include asputtered conductive material that transmits visible light, such asindium-tin-oxide (ITO), or the conductive integrated barrier layer 90may include conductive filaments, nanowires, or nanotubes, therebyproviding the needed combination of electrical conductivity,light-transmission, and flexibility. Alternatively, the conductiveintegrated barrier layer 90 may incorporate one of morelight-transmissive conductive polymers, such aspoly(3,4-ethylenedioxythiophene) (PEDOT), which may be solubilized withthe addition of polystyrene sulfonate. The conductive integrated barrierlayer 90 typically also includes a moisture blocking material, such aswaterproof materials such as inorganic ceramics, organic polymers ororganic/inorganic composites. The inorganic ceramics, for example,include silicon oxide (SiOx) or silicon nitride (SiNx). The organicpolymers, for example, include parylene or polypropylene, orpolyethylene terephthalate (PET). The organic/inorganic composites, forexample, include amorphous silicon/parylene composite, orpolypropylene/polyacrylate/aluminum composite. In some embodiments, theconductive integrated barrier layer 90 may also include an integratedcolor filter array (CFA), e.g., of the type described in U.S. Pat. No.10,209,556, which is incorporated by reference herein in its entirety.Alternative constructions of color filter arrays incorporated into theconductive integrated barrier layer 90 are also possible, for example,using stacked thin colored films, offset printing, or lithographicprinting. CFAs for such devices may include four colored subpixels, suchas red, green, blue, and clear (white), three colored subpixels, such asred, green, and blue, or stripes running top to bottom, left to right,or diagonal. Combinations of subpixels and stripes are possible, and thecolor sets are not limited to red, green, and blue, as other suitablecolor sets are available, provided the combination of colors provides anacceptable palette of colors to reproduce color images.

In foldable displays 10, the flexible backplane 75 includes a pluralityof driving electrodes on a flexible substrate. In FEPIDs the electricaldriving waveforms are transmitted to the flexible backplane 75, whichtypically includes pixel electrodes, via flexible conductive traces (notshown) that are coupled to thin-film transistors (TFTs) that allow thepixel electrodes to be addressed in a row-column addressing scheme. Inother embodiments, the pixel electrodes of the flexible backplane 75 maybe directly driven, that is, each pixel is directly turned on and off bya driver circuit. In some embodiments, the conductive integrated barrierlayer 90 is merely grounded and the image driven by providing positiveand negative potentials to the flexible backplane pixel electrodes,which are individually addressable. In other embodiments, a potentialmay also be applied to the conductive integrated barrier layer 90 toprovide a greater variation in the fields that can be provided betweenthe conductive integrated barrier layer 90 and the flexible backplane75. Active matrix flexible backplanes suitable for use in the inventionare available from, e.g., FlexEnable (Cambridge, UK) and othersuppliers. Flexible active matrix backplanes typically use thin films ofconductive organic materials to create flexible thin-film transistors.More details on suitable flexible backplanes and backplane componentscan be found in U.S. Pat. Nos. 7,223,672, 7,902,547, and 8,431,941,which are incorporated herein by reference in their entireties.

In many embodiments, the flexible backplane 75 will include an activematrix for image driving. In an active matrix arrangement, each pixelelectrode is coupled to a thin-film transistor patterned into an array,and connected to elongate row electrodes and elongate column electrodes,running at right angles to the row electrodes. In some embodiments, thepixels comprise transistors fabricated from metal oxides or conductivepolymeric material. In some embodiments, the pixels are flexible. Insome embodiments, the pixels are rigid, but because the substrate andthe traces between the pixels are flexible, the backplane can flexsufficiently to create a flexible backplane. Typically, a data driver isconnected to the column electrodes and provides source voltage to allTFTs in a column that are to be addressed. In addition, a scanningdriver is connected to the row electrodes to provide a bias voltage thatwill open (or close) the gates of each TFT along the row. The gatescanning rate is typically ˜60-100 Hz. It is understood that theassignment of “row” and “column” electrodes is somewhat arbitrary andthat a TFT array could be fabricated with the roles of the row andcolumn electrodes interchanged. In some embodiments, the TFT array issubstantially flexible, however individual components, such asindividual pixel transistors or driver circuits may not be flexible. Theflexible traces for supply voltages to the individual pixels may beformed from flexible materials, such as conductive polymers, or polymersdoped with conductive materials such as metal particles, nanoparticles,nanowires, nanotubes, graphite, and graphene.

The invention additionally includes a foldable electrophoretic displaymodule 15, as shown in FIG. 1B. Such a foldable display module 15 can bemanufactured as a stand-alone foldable electrophoretic displaycomponent, whereby it can be shipped to various manufacturers who canintegrate the module 15 into a foldable electrophoretic display, e.g.,of the type described below with respect to FIGS. 2A, 2B, and 3. Afoldable display module 15 is typically conditioned and sealed beforeshipment so that it can be laminated to additional components, e.g., afront light or capacitive touch sensor or an electromagnetic resonancesensing layer, both of which are discussed below. To maintain theintegrity of the module 15, the module typically includes an edge seal93 or the type that is typical with electrophoretic displays. For agreater description of EPID edge seals, see U.S. Pat. No. 7,554,712,which is incorporated herein by reference in its entirety.

A flexible display module 15 includes the support plate 50 havingmaterial voids 55 in a central folding zone 57, a layer of low-modulusadhesive 60, a flexible backplane 75 that spans the central folding zone57, a layer of electrophoretic display media 80, and a conductiveintegrated barrier layer 90, which includes the features of both alight-transmissive electrode and a moisture barrier. As shown in moredetail in FIG. 1B, the layer of electrophoretic display media 80 mayinclude microcapsules 88, holding electrophoretic pigment particles 83and 87 and a solvent 82, with the microcapsules 88 dispersed in apolymeric binder 81. Nonetheless, it is understood that theelectrophoretic medium (particles 83 and 87 and solvent 82) may beenclosed in microcells (microcups) or distributed in a polymer without asurrounding microcapsule (e.g., PDEPID design described above).Typically, the pigment particles 83 and 87 are controlled (displaced)with an electric field produced between the conductive integrate barrierlayer 90 and the flexible backplane 75. A module of the invention mayadditionally include a top protective sheet 95, which may be a hardenedtransparent anti-glare covering made from a polymer, such as apolyacrylate or a polyimide. The top protective sheet 95 may beintegrated into the edge seal 93, or the top protective sheet 95 mayactually envelope the edge seal to provide an extra degree ofenvironmental protection for the electrophoretic display layer 80 andthe flexible backplane 75. In some instances a module 15 willadditionally include a protection layer 70 between the low-modulusadhesive 60 and the flexible backplane 75 to prevent ingress of thelow-modulus adhesive into the flexible backplane 75 materials. Theprotection layer 70 may be a thin polymer layer, such as polyethyleneterephthalate, or the protection layer 70 may be a flexible dielectriclayer applied to the “back” of the flexible backplane 75, such asparylene.

While EPID media are described as “black/white,” they are typicallydriven to a plurality of different states between black and white toachieve various tones or “greyscale.” Additionally, a given pixel may bedriven between first and second grayscale states (which include theendpoints of white and black) by driving the pixel through a transitionfrom an initial gray level to a final gray level (which may or may notbe different from the initial gray level). The term “waveform” will beused to denote the entire voltage against time curve used to effect thetransition from one specific initial gray level to a specific final graylevel. Typically, such a waveform will comprise a plurality of waveformelements; where these elements are essentially rectangular (i.e., wherea given element comprises application of a constant voltage for a periodof time); the elements may be called “pulses” or “drive pulses.” Theterm “drive scheme” denotes a set of waveforms sufficient to effect allpossible transitions between gray levels for a specific display. Adisplay may make use of more than one drive scheme; for example, theaforementioned U.S. Pat. No. 7,012,600 teaches that a drive scheme mayneed to be modified depending upon parameters such as the temperature ofthe display or the time for which it has been in operation during itslifetime, and thus a display may be provided with a plurality ofdifferent drive schemes to be used at differing temperature etc. A setof drive schemes used in this manner may be referred to as “a set ofrelated drive schemes.” It is also possible to use more than one drivescheme simultaneously in different areas of the same display, and a setof drive schemes used in this manner may be referred to as “a set ofsimultaneous drive schemes.”

Foldable Electrophoretic Display Including Touch Sensing andDigitization Layer

An advanced embodiment of a foldable electrophoretic display (FEPID)using a design of the invention is shown in FIG. 2A and FIG. 2B. TheFEPID 100 roughly resembles a foldable version of a premium two panelelectrophoretic tablet, of the type sold by GVIDO Music Co., LTD.(Tokyo, Japan) as a digital ePaper music score. However, the instantinvention allows the folding region to be active, making the reading andwriting experience continuous across the spine. The FEPID 100 designshown in FIGS. 2A and 2B need not be as large as two full A4 sheets, andmay be the size of a singular A4 sheet when opened flat, and providingtwo panes of approximately 100 mm×150 mm when held partially opened as abook. The FEPID 100 may include all of the functionality that iscurrently expected in such a device including WIFI communication,BLUETOOTH, a color adjusting front-light, stylus recognition and writingreproduction, touch sensing, and color. The color electrophoreticdisplay may include a color filter array used with conventional blackand white ink, or the color electrophoretic display may incorporateadvanced electrophoretic display technology from E Ink Corporation, suchas Advanced Color e Paper (ACEP™) or E Ink Spectra™. Details of ACeP™and E Ink Spectra™ can be found at U.S. Pat. Nos. 9,921,451 and10,032,419, which are incorporated by reference herein in theirentireties.

Returning to FIG. 2A, the foldable electrophoretic display (FEPID) 100includes a housing 110 extending around the backside of the display 100,with a break in the middle allowing the display 100 to fold like a book.The housing 110 covers a chassis 120 including two plates that provideshock resistance for the display 100 and prevent back-bending, asdescribed previously with respect to FIG. 1A. The housing may be adurable polymer, such as nylon, or it may be a “finished” material suchas wood or leather. While not shown in FIG. 1A, the housing 110 may alsobe integrated into the chassis 120, and optionally coupled to a hinge(not shown) that provides a radius about which the chassis 120 folds.The housing 110 wraps around the display and finishes with a bezel 105,which may be above or flush with the top surface of the display 100. Inthe instance of FIG. 1A, the bezel 105 is above the top protective sheet195, which may be a hardened transparent anti-glare covering made from apolymer, such as a polyacrylate or a polyimide.

The embodiment shown in FIG. 2A includes two pressure touch sensorlayers 130, above each of the chassis plates 120. Because of the use ofa thin support plate 150 with material voids 155, and a low-modulusadhesive 160 between the flexible backplane 175 and the support plate150, there is sufficient compressive force by a user pushing on theprotective sheet 195 with a finger for the pressure touch sensor layers130 to be activated. Such pressure-sensitive layers may includemicro-deformable piezoresistive sensors, which are quite thin and arecommercially available from Uneo Inc. (New Taipei City, Taiwan).Alternative thin, touch sensitive technology, such as QTC force-sensingtechnology pioneered by Peratech (Richmond, United Kingdom) may also beused for the pressure touch sensor layers 130.

The display 100, of FIG. 2 additionally incorporates a flexibleelectromagnetic resonance (EMR) sensor layer 140 to sense an activestylus, which can be used for e.g., handwriting capture, sketching,mark-up, or manipulating objects on the display. Flexible EMR layers 140may include stacked loops of wires in a flexible medium, therebyallowing proximity sensing of an active or a passive stylus. Suitablestyluses are available from, e.g., Wacom (Kazo, Japan). The EMR layer140 may be a single contiguous unit, or it may be a collection ofindividual EMR layers 140. In an alternative embodiment, not shown inFIG. 2A, the EMR layer 140 may include two separate semi-rigid EMRlayers of the type commercially available from Wacom, with a smallerarea of a specialty flexible EMR that spans the central folding zone. Insome embodiments, one or both surfaces of the flexible EMR layer 140will be rough, or have a roughened surface 145, to help the EMR layerstay relatively flat and only move side to side, rather than up anddown, in the view of FIG. 2A.

In the middle of the foldable display 100 is the support plate 150having material voids 155 in a central folding zone. As discussed ingreater detail with respect to FIGS. 4A, 4B, 5A, and 5B, the supportplate can be made from a variety of materials, such as polymers, metal,e.g., stainless steel, carbon fiber, or wood veneers. In the embodimentof FIG. 2A, the support plate 150 comprises a non-conductive polymer,such as polyethylene terephthalate, which does not interfere withelectromagnetic resonance position sensing between flexible EMR layer140 and a stylus used on the top surface of the display 100. The supportplate is typically between 250 μm and 50 μm in thickness. The centralfolding zone for the support plate 150 is not specifically marked inFIG. 2A for simplicity, but it is roughly the area where the voids 155have been removed from the support plate 150. The central folding zonemay be less than 20% of the total surface area of the support plate 150,e.g., less than 10% of the total surface area of the support plate 150,e.g., less than 5% of the total surface area of the support plate 150.

As discussed above, a low-modulus adhesive layer 160 is disposed betweenthe support plate 150 and the flexible backplane 175. Finally, in someembodiments, a protection layer 170 may be disposed between the flexiblebackplane 175 and the low-modulus adhesive layer 160 to protect theflexible backplane 175 from corrosion or electrical malfunction due tocontact with the low-modulus adhesive layer 160, which may includeconductive material or solvents that may attack the flexible backplane175. However, with the choice of suitable low-modulus adhesive layer160, it may be unnecessary to include protection layer 170. (Elements180, 181, 182, 183, 187, 188, and 190 are the electrophoretic displaylayer 80, the polymer binder 81, the electrophoretic medium solvent 82,the first particle set 83, the second particle set 87, the capsule wall88, and the conductive integrated barrier layer 90, as described abovewith respect to FIG. 1B.)

In a commercial application, it is likely that additional componentswill be present in a foldable electrophoretic display (FEPID) 101, whenthe FEPID includes EMR sensing layer 140 and the pressure touch sensorlayers 130, as shown in FIG. 2B. Firstly, as discussed with respect toFIG. 1B, it is likely that a hinge 125 will be included to facilitateopening and closing of the two plates of the chassis 130. The hinge 125is merely exemplary and a variety of alternative hinges may be used.Additionally, it is typical that one or more additional layers oflow-modulus adhesive will be added between the various layers of theFEPID display 101 to help the display 101 to retain a smooth shapedespite repeated opening and folding. For example, a first intermediatelow-modulus adhesive layer 133 may be disposed between the pressuretouch sensor layer 130 and the flexible EMR layer 140. A secondintermediate low-modulus adhesive layer 143 may be disposed between theflexible EMR layer 140 and the support plate 150. Notably, the first andsecond intermediate low-modulus adhesive layers need not span the entirewidth of the display, i.e., from the left side to the right side in FIG.2B. This partial disposition of low-modulus adhesive will providegreater void space during the folding process, resulting in lesspressure on the electrophoretic display layer 180 at the fold, andreducing the likelihood of failure or delamination with multiple folds.In addition to low-modulus adhesive layers 143 and 147, high-modulusadhesives, such as polyurethanes or polyacrylates may be used on theopposing side of the FEPID 101 to assure that the layers of the display101 are locked together and that most of the lateral movement takesplace on one side of the display, while the other side stays firm. Thatis, a first intermediate high-modulus adhesive layer 137 may be disposedbetween the pressure touch sensor layer 130 and the flexible EMR layer140, while a second intermediate high-modulus adhesive layer 147 may bedisposed between the flexible EMR layer 140 and the support plate 150.The high-modulus adhesives help the alignment of the various layers tobe maintained throughout repeated opening and closing cycles.

Foldable Electrophoretic Display Including a Front Light and CapacitiveTouch Sensing

A foldable electrophoretic display (FEPID) 200 including a capacitivetouch sensing layer 294, a front light plate 292, and a light source 291is illustrated in FIG. 3. Many of the component parts of FEPID 200 arethe same as FEPID 100 described with respect to FIG. 2A. FEPID 200includes a housing 210 extending around the backside of the display 200,with a break in the middle allowing the display 200 to fold like a book.The housing 210 covers a chassis 220 including two plates that provideshock resistance for the display 200 and prevent back-bending, asdescribed previously with respect to FIG. 2A. The housing 210 wrapsaround the display and finishes with a bezel 205, which may be above orflush with the top surface of the display 200. In the instance of FIG.3, the bezel 105 is above the top protective sheet 195, which may be ahardened transparent anti-glare covering made from a polymer, such as apolyacrylate or a polyimide.

In the middle of the foldable display 200 is a support plate 250 havingmaterial voids 255 in a central folding zone. As discussed in greaterdetail with respect to FIGS. 4A, 4B, 5A, and 5B, the support plate canbe made from a variety of materials, such as polymers, metal, e.g.,stainless steel, carbon fiber, or wood veneers. In the embodiment ofFIG. 3, the support plate 250 may use conductive or non-conductivematerials because there is no sensing mechanism behind the support plate250. The support plate is typically between 250 μm and 50 μm inthickness. The central folding zone for the support plate 250 is notspecifically marked in FIG. 3 for simplicity, but it is roughly the areawhere the voids 255 have been removed from the support plate 250. Alow-modulus adhesive layer 260 is disposed between the support plate 250and the flexible backplane 275. Finally, in some embodiments, aprotection layer 270 may be disposed between the flexible backplane 275and the low-modulus adhesive layer 260 to protect the flexible backplane275 from corrosion or electrical malfunction due to contact with thelow-modulus adhesive layer 260, which may include conductive material orsolvents that may attack the flexible backplane 275. Elements 280, 281,282, 283, 287, 288, and 290 are the electrophoretic display layer 80,the polymer binder 81, the electrophoretic medium solvent 82, the firstparticle set 83, the second particle set 87, the capsule wall 88, andthe conductive integrated barrier layer 90, as described above withrespect to FIG. 1B.)

In the FEPID 200, the sensing is achieved with a flexible capacitivetouch layer 294 disposed near the surface of the display 200, andprotected a top protective sheet 95, which may be a hardened transparentanti-glare covering made from a polymer, such as a polyacrylate or apolyimide. The flexible capacitive touch layer 294 may provide bothtouch input by a user's finger and stylus writing with a capacitivetouch pen, such as offered by N-Trig Technologies (Tel Aviv, Israel).Because the flexible capacitive touch layer 294 is between the viewerand the electrophoretic display medium the flexible capacitive touchlayer 294 must also be light transmissive. The FEPID 200 shown in FIG. 3additionally includes a front light plate 292, which is illuminated byone or more light sources 291, which may be light-emitting diodes (LED)that are white, or have a range of LED colors to enable color adjustmentof the front light depending upon the user's needs.

Accordingly, it can be seen that a module 15 of the invention can beincorporated into a variety of foldable electrophoretic display designs.However, the designs are not limited to FIGS. 2A, 2B, and 3. Rather awide variety of different digitizing systems can be used with thefoldable electrophoretic display modules shown here. For example, activeelectrostatic sensing (Wacom) may be used with the invention, orinfrared sensing, as available from Planar Technologies (Hillsboro,Oreg.). Furthermore, various foldable electrophoretic display devicesmay be integrated into an ecosystem of devices, including WIFI,BLUETOOTH, ZIGBEE or the like.

Creation of Support Plate with Material Voids

As discussed previously, a support plate (50, 150, 250) for theinventions described herein may be made from polymers, metal, e.g.,stainless steel, carbon fiber, or wood veneers. In the instances where asensing layer will be disposed below the support plate (50, 150, 250)the support plate (50, 150, 250) is best achieved with a non-conductivepolymer, such as polyethylene terephthalate, which does not interferewith electromagnetic resonance position sensing between flexible EMRlayer 140 and a stylus used on the top surface of the display 100, asdescribed with respect to FIG. 2A. However, for instances in which thereis no sensing on the backside of the support plate (50, 150, 250), as inFIG. 3, it is not necessary for the support plate (50, 150, 250) to benonconductive. Accordingly, alternatives such as stainless steel can beused for FIG. 3. In most instances, the support plate is typicallybetween 250 μm and 50 μm in thickness, for example between 150 μm and100 μm in thickness.

Two embodiments of a support plate having material voids in a centralfolding zone are shown in FIGS. 4A, 4B, 5A, and 5B (FIG. 4A is a sideview of the first embodiment while FIG. 4B is a top view. FIG. 5A is aside view of the second embodiment while FIG. 5B is a top view.) Tocreate the embodiment of FIG. 4A, a singular piece of material 451 canbe milled, cut, embossed, ablated, or laser machined to create voids455, which allow the support plate 450 to bend in the desired directionrepeatedly and with little force. The stiffness of the support plate 450can be tuned by selecting an appropriate depth of the void relative tothe total thickness of the work piece 451. The depth of the voids neednot be identical across the piece and may be cut, e.g., as a Gaussiandistribution with the greatest depth in the center and progressivelyshallower cuts moving away from the center. The central folding zone forthe support plate 450 is not specifically marked in FIG. 4A forsimplicity, but it is roughly the area where the voids 455 have beenremoved from the support plate 450. The central folding zone may be lessthan 20% of the total surface area of the support plate 450, e.g., lessthan 10% of the total surface area of the support plate 150, e.g., lessthan 5% of the total surface area of the support plate 450.

Support plates having material voids are not limited to the cut patternshown in FIGS. 4A and 4B. For example, a workpiece 551 may have a seriesof voids 555 cut from the workpiece 551 to create a central foldingzone. In the embodiment of FIGS. 5A and 5B, the support plate may bemetal, in which case the voids may be stamped or milled from theworkpiece 551. Alternatively, if the workpiece 551 is a polymer orcarbon fiber, the voids 555 may be created with laser cutting.

DEFINITIONS

The term “electro-optic”, as applied to a material or a display, is usedherein in its conventional meaning in the imaging art to refer to amaterial having first and second display states differing in at leastone optical property, the material being changed from its first to itssecond display state by application of an electric field to thematerial. Although the optical property is typically color perceptibleto the human eye, it may be another optical property, such as opticaltransmission, reflectance, luminescence or, in the case of displaysintended for machine reading, pseudo-color in the sense of a change inreflectance of electromagnetic wavelengths outside the visible range.

The term “gray state” or “gray scale” is used herein in its conventionalmeaning in the imaging art to refer to a state intermediate two extremeoptical states of a pixel, and does not necessarily imply a black-whitetransition between these two extreme states. For example, several of theE Ink patents and published applications referred to below describeelectrophoretic displays in which the extreme states are white and deepblue, so that an intermediate “gray state” would actually be pale blue.Indeed, as already mentioned, the change in optical state may not be acolor change at all. The terms “black” and “white” may be usedhereinafter to refer to the two extreme optical states of a display, andshould be understood as normally including extreme optical states whichare not strictly black and white, for example the aforementioned whiteand dark blue states. The term “monochrome” may be used hereinafter todenote a drive scheme which only drives pixels to their two extremeoptical states with no intervening gray states.

Some electro-optic materials are solid in the sense that the materialshave solid external surfaces, although the materials may, and often do,have internal liquid- or gas-filled spaces. Such displays using solidelectro-optic materials may hereinafter for convenience be referred toas “solid electro-optic displays”. Thus, the term “solid electro-opticdisplays” includes rotating bichromal member displays, encapsulatedelectrophoretic displays, microcell electrophoretic displays andencapsulated liquid crystal displays.

The terms “bistable” and “bistability” are used herein in theirconventional meaning in the art to refer to displays comprising displayelements having first and second display states differing in at leastone optical property, and such that after any given element has beendriven, by means of an addressing pulse of finite duration, to assumeeither its first or second display state, after the addressing pulse hasterminated, that state will persist for at least several times, forexample at least four times, the minimum duration of the addressingpulse required to change the state of the display element. It is shownin U.S. Pat. No. 7,170,670 that some particle-based electrophoreticdisplays capable of gray scale are stable not only in their extremeblack and white states but also in their intermediate gray states, andthe same is true of some other types of electro-optic displays. Thistype of display is properly called “multi-stable” rather than bistable,although for convenience the term “bistable” may be used herein to coverboth bistable and multi-stable displays.

It will be apparent to those skilled in the art that numerous changesand modifications can be made in the specific embodiments of theinvention described above without departing from the scope of theinvention. Accordingly, the whole of the foregoing description is to beinterpreted in an illustrative and not in a limitative sense.

1. An electrophoretic display module, comprising: a support plate havingmaterial voids in a central folding zone; a layer of low-modulusadhesive adjacent the support plate; a flexible backplane that spans thecentral folding zone and is adjacent the layer of low-modulus adhesive;a layer of electrophoretic display media adjacent the flexiblebackplane; and a conductive integrated barrier layer including alight-transmissive electrode and a moisture barrier.
 2. Theelectrophoretic display module of claim 1, further comprising aprotection layer between the layer of low-modulus adhesive and theflexible backplane.
 3. The electrophoretic display module of claim 1,wherein the flexible backplane comprises an active matrix oforganic-thin-film-transistors.
 4. The electrophoretic display module ofclaim 1, further comprising an edge seal coupled to the flexiblebackplane, the layer of electrophoretic display media, and theconductive integrated barrier.
 5. The electrophoretic display module ofclaim 1, wherein the layer of electrophoretic display media is containedin a layer of microcells.
 6. The electrophoretic display module of claim1, wherein the layer of electrophoretic display media is contained inmicrocapsules and the microcapsules are held in place by a polymerbinder.
 7. The electrophoretic display module of claim 1, furthercomprising a protective sheet adjacent the conductive integratedbarrier.
 8. The electrophoretic display module of claim 7, furthercomprising an edge seal coupled to the flexible backplane, the layer ofelectrophoretic display media, the conductive integrated barrier, andthe protective sheet.
 9. The electrophoretic display module of claim 1,wherein the support plate comprises a non-conductive polymer.
 10. Theelectrophoretic display module of claim 9, wherein the support plate isbetween 250 μm and 50 μm in thickness.
 11. A foldable electrophoreticdisplay configured to interact with a stylus, the foldable displaycomprising: the electrophoretic display module of claim 9; a protectivesheet coupled to the conductive integrated barrier; an electromagneticresonance (EMR) sensor layer adjacent to the support plate a foldablechassis adjacent to the EMR sensor layer; a housing surrounding thefoldable chassis and providing a bezel contacting the protective sheet,and allowing a user to view the electrophoretic display medium throughthe protective sheet.
 12. The foldable electrophoretic display of claim11, further comprising an intermediate layer of a low-modulus adhesivedisposed between the EMR sensor layer and the support plate.
 13. Thefoldable electrophoretic display of claim 12, further comprising anintermediate layer of a high-modulus adhesive disposed between the EMRsensor layer and the support plate.
 14. The foldable electrophoreticdisplay of claim 13, wherein the intermediate layer of a low-modulusadhesive and the intermediate layer of a high-modulus adhesive do notspan the central folding zone.
 15. The foldable electrophoretic displayof claim 11, further comprising a touch sensitive layer disposed betweenthe EMR sensor layer and the foldable chassis.
 16. The foldableelectrophoretic display of claim 11, wherein the conductive integratedbarrier additionally comprises a color filter array (CFA).
 17. Afoldable electrophoretic display configured to interact with a stylus,the foldable display comprising: the electrophoretic display module ofclaim 9; a flexible front light plate coupled to the conductiveintegrated barrier; a flexible capacitive touch layer adjacent to theflexible front light plate; a protective sheet adjacent to the flexiblecapacitive touch layer; a foldable chassis adjacent to the supportplate; and a housing surrounding the foldable chassis and providing abezel contacting the protective sheet, and allowing a user to view theelectrophoretic display medium through the protective sheet.
 18. Thefoldable electrophoretic display of claim 17, further comprising anintermediate layer of a low-modulus adhesive disposed between thefoldable chassis and the support plate.
 19. The foldable electrophoreticdisplay of claim 18, further comprising an intermediate layer of ahigh-modulus adhesive disposed between the foldable chassis and thesupport plate.
 20. The foldable electrophoretic display of claim 19,wherein the intermediate layer of a low-modulus adhesive and theintermediate layer of a high-modulus adhesive do not span the centralfolding zone.